The invention relates to a method for producing of fuel briquettes by hot pressing a mixture including a fine grained coal which softens at the pressing temperature and a component which does not or hardly soften at the pressing temperature whereby the starting components prior to their being mixed, are heated to different temperatures by first introducing the non-softening component, as viewed in the flow direction, into a flow of a heating gas and thereafter introducing the softening component into the flow of a heating gas. After the heating of the components they are separated from the gas flow.
The quality properties in the production of hot briquettes such as their rigidity and low smoke production, do not depend only on the original properties of the starting raw materials, but are determined to a substantial extent also by the condition in which the raw materials are at the time of pressing.
In the known methods for producing fuel briquettes, efforts are made to achieve certain quality characteristics by means of defined raw material conditions of the mixture to be pressed, said conditions being achieved by a thermal disintegration. The techniques practiced heretofore, for the thermal treatment of solid, powderized, or granular fuels to degas or gasify such fuels, started from the assumption that it is necessary to first subject the substances to be treated in separate process steps to drying and milling to obtain a surface area as large as possible. The so treated materials were then separated according to size and then subjected to the actual thermal process. The raw materials are supposed to take on the desired state or condition by a determined heating and degasification of the starting components as well as by a further degasification of the mixture prior to the pressing and within a determined temperature time function.
The known method of oxygen enrichment, that is a process employing oxygen in proportions above the stoichiometric proportion, was employed with the intent to decompose coking hard coal in such a manner that the coal would lose its coking capability, which is to some extend a hindrance in the following process steps. Such oxygen enrichment of the smoke gases, which in addition to functioning as the heat transfer means also performs the function of a carrier medium, resulted in addition to the desired destruction of the coking characteristic, in an undesirable and uneconomical carbon combustion.